1. Field of the Invention
The present invention relates to a semiconductor device having a memory element, and particularly relates to the semiconductor device where an electrostatic discharge protection circuit is provided to a terminal for recording and writing information in the memory element.
2. Description of the Related Art
Conventionally, semiconductor devices where memory elements are arranged on semiconductor substrates have been developing increasingly.
Various applications of the memory elements are present, but they are used in semiconductor devices for liquid discharge. The memory elements are used for recording temperature dependency of liquid discharge property or the residual quantity of liquid in semiconductor devices.
In applications where the large number of bits are not necessary and once-writing is carried out, fuse ROMs are used because of its simplicity of the manufacturing process (see Japanese Patent Application Laid-Open No. 2000-343721). When the fuse ROMs are used, electrostatic discharge protection circuits which prevent electrostatic breakdown caused when a high voltage is applied to input/output terminals due to static electricity (for example, Japanese Patent Application Laid-open No. S62-152155 (1987)).
In the invention of Japanese Patent Application Laid-open No. 2000-343721, at the time of writing in a fuse ROM, the fuse is cut off, but if the high amount of energy is not instantaneously applied to the fuse at this time, cut residue or the like occurs, thereby occasionally causing false detection.
The high electric current should be allowed to flow in order to cut the fuse stably, but in this case, a voltage which is applied to terminals for recording/redding information becomes inevitably high.
On the contrary, at the time of reading information, very high voltage does not have to be applied. Concretely, a voltage of 20 to 30 V is applied to the terminal at the time of writing, and a voltage of several V is applied at the time of reading.
In such a configuration, when the voltage of the terminal changes greatly, a function as electrostatic discharge protection element should be provided without allowing an electric current to flow, and thus there is room to examine the design.
It is an object of the present invention to provide a semiconductor device having an electrostatic discharge protection circuit which is suitable for the case where voltages with large difference is applied.